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An alternative approach to match the turbine to the characteristics of an owc wave power plant

Abstract:

Oscillating water column wave power plants (OWC) are widely used in the ocean wave energy conversion. It is universally accepted that for a good efficiency of the plant, the turbine and the chamber should matched each other according to the wave climate site. The damping applied by the turbine has appreciable effects on the chamber performance of the OWC plant. In this work an alternative methodology is presented to couple the chamber and the turbine. The methodology made a whole dimensional analysis of the OWC plant. It has been assumed: incompressible flow, sinusoidal wave height variation and neglected Reynolds influence. The wave data for the plant site and the chamber geometry are the input data. The behavior of the chamber for the prevailing sea conditions is numerically simulated. From numerical results, the pneumatic power coefficient is represented versus the damping coefficient. Then, the optimum damping is set. Once the optimum damping is found the target is to determine a turbine which matches this damping. Considering the quasi-steady assumption, numerical results were used to simulate the turbine performance under unsteady flow conditions. The dimensionless performance curves of any kind of turbine are the input data to determine the diameter and rotational speed. The calculation of the diameter is based on the pressure drop caused by the turbine on the OWC. The last step is to determine the rotational speed, it is calculated to achieve that the turbine operates close to its maximum efficiency. This methodology is worked out to compare the size and the rotational speed for different kinds of turbines. Also the influence of sea states changes in the characteristics of the optimum turbine is studied. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).